Sewing machine feeding mechanism



March 6, 1962 R. E. JOHNSON 3,023,722

SEWING MACHINE FEEDING MECHANISM Filed Jan. 25, 1960 '3 Sheets-Sheet 1INVENTOR. RALPH E. Jamvsozv BY WZI'TTORNEY WITNESS March 6, 1962 R. E.JOHNSON SEWING MACHINE FEEDING MECHANISM '3 Sheets-Sheet 2 Filed Jan.25, 1960 INVEN TOR BY RALPH E. JOHNSON 6 ZTORNEY WITNESS March 6, 1962R. E. JOHNSON SEWING MACHINE FEEDING MECHANISM 3 Sheets-Sheet 3 FiledJan. 25, 1960 RALPH E. JOHNSON BY ATTORNEY WITNESS United States Patent3,023,722 SEWING MACHINE FEEDING MECHANISM Ralph E. Johnson,Mountainside, N.J., assignor to The Singer Manufacturing Company,Elizabeth, N.J., a corporation of New Jersey Filed Jan. 25, 1960, Ser.No. 4,429 3 Claims. (Cl. 112210) The present invention relates to sewingmachines and particularly to a feeding mechanism for sewing machines.

The object of this invention is to provide a feeding mechanism forsewing machines in which the rise of the feed dog above the throat plateis adjustable and wherein the adjustment will have a minimum effect uponthe overall feed lift motion of the feed dog and thereby will notappreciably vary the path of motion of the feed dog.

Further objects of this invention are to provide such a feed adjustmentthat is economical, simple to adjust, and dependable and durable.

Having in mind the above and other objects that will be evident from anunderstanding of this disclosure, the invention comprises the devices,combinations and arrangements of parts as illustrated in the presentlypreferred embodiment of the invention which is hereinafter set forth insuch detail as to enable those skilled in the art readily to understandthe function, operation, construction and advantages of it when read inconjunction with the accompanying drawings in which:

FIG. 1 is a vertical sectional view longitudinally of a sewing machineembodying the present invention,

FIG. 2 is a bottom plan view of the bed of the sewing machine of FIG. 1,

FIG. 3 is a fragmentary detail sectional view substantially on the line33 of FIG. 2,

FIG. 4 is a sectional view substantially on the line 44 of FIG. 2,

FIG. 5 is a sectional view substantially on the line 5-5 of FIG. 2,

, FIG. 6 is a fragmentary detail sectional view similar to FIG. 3 but ona larger scale and illustrating the feed lift cam in differentpositions,

FIG. 7 is a fragmentary detail sectional view substantially on the line77 of FIG. 3.

The present invention is illustrated as embodied in the sewing machineforming the subject matter of the copending United States patentapplication of Johnson, Serial No. 4,430, filed January 25, 1960,wherein the machine is fully disclosed and to which reference may be hadfor a more complete understanding of the machine.

With reference to the drawings, there is illustrated a sewing machinehaving a frame including a bed 1, a standard 2 rising from one end ofthe bed and carrying a bracket arm 3 terminating in a head 4 overhangingthe bed 1. The top of the bed 1 is formed by a bed plate 5. Journaledlongitudinally of the bracket arm 3 is a rotary main shaft 6 that isdriven by an electric motor 7 mounted in the standard 2 and connected bya belt 8 to a hand wheel 9 secured on the end of the main shaft 6.

The stitching mechanism of the machine comprises a needle bar 10 mountedin the head 4 for endwise reciprocation and driven from the main shaft 6by a crank 11 and link 12. Beneath the needle bar 10, the bed plate 5has a throat plate 13, the upper surface of which, together with theupper surface of the bed plate 5, defines the work supporting surface ofthe machine. At its lower end the needle bar 10 carries a needle 14which, upon endwise reciprocation of the needle bar 10, penetrates thethroat plate 13 and cooperates with a vertical axis oscillating book 15in the bed 1 and thereby defines the point of stitch formation on thework supporting sur face of the machine. The hook 15 is mounted upon ahook shaft 16 journaled in a supporting wall 17 integral 3,023,722Patented Mar. 6, 1962 with the bed plate 5. Oscillation is imparted tothe hook shaft 16 by a vertical axis shaft 18 journaled in the standard2 and connected by gears 19 and 20 to the main shaft 6. On the lower endof the shaft 18 is a crank 21 connected by a pitman 22 to one arm 23 ofa bell crank lever pivotally mounted intermediate its ends at 24 on thewall 17. The other arm 25 of the bell crank lever is connected by a link26 to a crank arm 27 secured to the lower end of the hook shaft 16.

Work is adapted to be advanced across the work supporting surface of themachine past the point of stitch formation by a four motion feedingmechanism comprising a feed bar 28 carrying a feed dog 29 operatingthrough feed dog slots in the throat plate 13 to engage the work.Journaled longitudinally of the bed at the front of the machine is afeed advance shaft 30 having rock arms 31 which are pivotally connectedto one end of the feed bar 28. Oscillation is imparted to the feedadvance shaft 3%} by an eccentric 32 on the main shaft 6 which isembraced by a fork on the upper end of a pitman 33. Intermediate itsends the pitman 33 has a laterally extending pin 34 extending into agroove 35 in a block 36 that is pivotally mounted in a transverse wallof the frame by means of a stud 37 and which includes a handle 38extending to a position accessible to the operator. At its lower end,the pitman 33 is connected to a crank arm 39 on the feed advance shaft30.

The feed lift mechanism comprises a feed lift shaft 40 journaled in therear of the bed 1 by cone shaped end bearings 41 in bearing lugs 42 and43. The one end of the feed lift shaft 40 has a crank arm 44 which atits free end is connected by a link 45 to the feed bar 28 for impartingfeed lift motions to the feed bar 28 upon oscillation of the feed liftshaft 40. At the other end of the feed lift shaft 40 there is a secondcrank arm 46 having a hub 47 at its free end that receives a cylindricalpin 43 mounted therein for turning adjustment, which turning isfacilitated by a screw driver slot 49 in the end thereof. The pin 48 issecured in its adjusted position by a set screw 50. Integral with thepin 48 is a stud 51 that is eccentric relatively to the axis of the pin48. A cam follower element 52 is pivotally mounted on the stud 51 and isheld thereon by a screw 53. The crank arm 46 is disposed to locate thecam follower element 52 in engagement with an axial displacement camsurface 54 formed on the upper surface of the crank 21. A coilcompression spring 55 is disposed between the crank arm 44 and theunderside of the bed plate 5 to bias the feed lift mechanism in thedirection to lower the feed bar 28 and to hold the cam follower element52 in tracking engagement with the cam surface 54. Thus, upon rotationof the crank 21 oscillation is imparted to the feed lift shaft 40.

The crank arm 44 is located adjacent to the lug 43 and is offset toposition the link 45 in a plane normal to the lug 43, and the crank arm46 is located adjacent to the lug 42 and is also offset to position thecam follower element 52 close to a plane normal to the lug 42. In thismanner substantially only torsional forces are applied to the shaft 40with a minimum of bending. The spring 55 also serves to pre-stress thefeed lift shaft 40 and thus minimizes torsional deflection of the shaft.

The feed path, which is the path of motion of a selected point on thefeed dog 29, is a function of the motion imparted to the feed dog by thefeed advance shaft 30 and the feed lift shaft 49. The desired feed pathand the timing of the feed motion are determined by basicconsiderations, for example, experience has shown that a particular riseof the feed dog above the throat plate produces an optimum engagement ofthe feed dog against the work, a relatively flat motion of the feed dogduring feeding is desirable, the feed must be operative while the needleis out of the work and preferably as late as possible in the cycle, andthe stitch length should be adjustable from Zero to a predeterminedmaximum. There are also various mechanical considerations, for example,the feed dog overlies the hook and must be designed so that there isalways adequate clearance between the two but which, at the same time,locates the hook as close as possible to the throat plate to provide aminimum needle bar stroke.

The mechanics of the system are designed to produce a desired feedmotion, which always represents some compromise that is determined bytrial and error to be best suited to the particular sewing machine. Onceestablished, the system cannot be freely changed since any changes inrelative timing between the feed lift motion and feed advance motion,and any changes in the amplitude of the motions will produce changes inthe feed path, thus destroying the designed optimum.

In the present machine, the timing of the feed advance is obtained bythe angular position of the eccentric 32 on the main shaft 6. Since theangular position of the crank 21 on the shaft 18 is fixed by the hookrequirements, the timing of the feed lift is obtained by theconfiguration of the cam surface 54 on the crank 21.

Having determined the feed lift motion necessary to obtain the desiredfeed path, it then becomes necessary to obtain the desired rise of thefeed dog 29 above the throat plate 13. This of course can be obtained bydesign and by maintaining strict manufacturing tolerances. However, thisis relatively expensive. To reduce manufacturing costs, it would bepreferable to provide a construction in which the manufacture of theelement is less critical and which is adjustable to obtain the desiredalignment of the parts. In the present machine, this adjustment has beenprovided by the eccentric stud 51. By rotating the pin 48, the feed liftis adjusted to provide the desired rise of feed dog 29 above the throatplate 13.

Such an adjustment in the feed must be made without altering themechanics 'of the system such as to vary the feed path significantly. Inthe operation of the present machine, the displacement of the camfollower element 52 by the cam surface 54 produces a certain angularmovement of the crank arm 46, the feed lift shaft 40 and the crank arm44, thus producing a certain feed lift motion. The angular movement ofthe crank arm 46 for any given displacement of the cam follower element52 is a dependent upon the location of the cam follower element 52radially relatively to the pivot axis of the crank arm 46, which is theaxis of the feed lift shaft 40. Shortening the radius will produce anincreased angular movement of the crank arm 46 while lengthening theradius will produce a reduced angular movement of the crank arm 46. Uponturning the pin 48 to adjust the rise of the feed dog, the eccentricstud 51 moves in an arc about the axis of the pin 48, thus having afirst component in a direction tangential to the arc of motion of thepin 48 about the axis of the feed lift shaft 40, which direction issubstantially vertical, and which component adjusts the feed lift motionto obtain the desired rise of the feed dog above the throat plate.However, the pin 48 also has a second component of motion that is in aplane that is substantially horizontal and is defined by the axis of thefeed lift shaft 40 and the pin 48. In effect this second componentvaries the lever arm between the axis of the 'feed shaft 40 and thepoint at which the force is applied by the cam follower element 52 tothe crank arm 46, i.e., the axis of the stud 51. Such a variation,changes the feed path.

To minimize the effect upon the effective length of the crank arm 46 bythe eccentricity of the stud 51, there is provided a stop shoulder 56 onthe crank arm 46 that is designed to be engaged by the edge 57 of thecam follower element 52 when the stud 51 is adjusted to its maximum andminimum positions in the direction tangential to I the arc of motion ofthe pin 48 about the axis of the feed anism such that the desiredsetting of the eccentric is at the midpoint of its arc of adjustment,and by making the eccentricity of the stud 51 more than the normallyrequired adjustment, a minimum of the undesired displacement of the stud51 is obtained. I J

The axis of rotation of the crank 21, which is the axis of the shaft 18,is normal to a horizontal plane containing the axis of the feed liftshaft 40, and the axis of the pin 48 is parallel to the axis of the feedlift shaft 40 and intersects the axis of the shaft 18. The cam surface54 on the crank 21 is planar and inclined to effect a displacement ofthe cam follower element 52 axially of the shaft 1-8. The cam followerelement 52 has a cam engaging surface 58 which is arcuate in a directionradially of said cam surface 54 and is defined by straight Pafa lines ina direction perpendicular to the radius of said cam surface. The camfollower element 52 is free to pivot about the axis of the stud 51 andbecause of the arcuate configuration of the cam engaging surface 58 andthe planar configuration of the cam surface 54 there is line contactbetween the cam engaging surface 58 and the cam surface 54 which, as thecam surface 54 is rotated and presents a differently inclined surface tothe surface 58, shifts the line of contact across the surface 58 betweenthe lines A and B, FIG. 6. In this manner there is provided asubstantial bearing between the surfaces 54 and 58 which can accommodatethe variations in the inclination of the cam surface 54 as it rotates,and also reduces wear on the cam engaging surface 58 by continuouslyshifting the line of engagement to distribute the wear over a largearea. At the same time, by virtue of the fact that the line of contactis a straight line perpendicular to the radius of the cam surface 54,the points of contact along the line are spaced different distances fromthe axis of the crank 21 e.g., as seen in FIG; 7, the ends of line ofcontact A engage the surface 54 along a circle C while the midpointengages along a circle D,- and the ends of the line B engage the camsurface 54 along a circle E while the midpoint engages along a circle F.Thus there is defined an annular engaging surface on the cam surface 54extending between the circles C and F, which again reduces wear bydistributing it over a large area.

Having thus described the nature of this invention what I claim hereinis:

:1. In a sewing machine having a frame including a bed having a worksupporting surface, stitching mechanism defining a point of stitchformation on said work supporting surface, and feeding mechanism foradvancing work past said point of stitch formation comprising a feedadvance shaft journaled in said bed and having a rock arm, a feed barpivotally connected to said rock arm, a feed dog carried by said feedbar, means for imparting oscillation to said feed advance shaft, a feedlift shaft journaled in said bed, means for connecting said feed liftshaft to said feed bar for imparting feed lift motions to said feed barupon oscillation of said feed lift shaft, a cam and cam follower meanson said feed lift shaft and cooperating with said cam for impartingoscillation to said feed lift shaft and for adjusting the rise of saidfeed dog relatively to said work supporting surface, comprising a crankarm on said feed lift shaft, a pin mounted in said crank arm for angularadjustment, means for releasably securing said pin in angularly adjustedposition in said crank arm, an eccentric stud on said pin, and a camfol-lower element mounted on said stud and engaging said cam and meansfor limiting angular adjustment of said pin substantially to one half ofone revolution in an are that at its midpoint has a tangent parallel toa tangent to the arc of the oscillation of the stud about the axis ofthe feed lift shaft.

2. In a sewing machine in accordance with claim 1 in Which said lastmentioned means comprises a stop shoulder on said crank against whichsaid cam follower element engages in its maximum and minimum positions.

3. In a sewing machine having a frame including a bed having a worksupporting surface, stitching mechanism defining a point of stitchformation on said Work supporting surface, and feeding mechanism foradvancing work past said point of stitch formation comprising a feedadvance shaft journaled in said bed and having a rock arm, a feed barpivotally connected to said rock arm, a feed dog carried by said feedbar, means for imparting oscillation to said feed advance shaft, a feedlift shaft journaled in said bed, means for connecting said feed liftshaft to said feed bar for imparting feed lift motions to said feed barupon oscillation of said feed lift shaft, a cam mounted on an axisnormal to a plane containing the axis of said feed shaft and having anaxial displacement planar cam surface, and cam follower means on saidfeed lift shaft and cooperating with said cam surface for impartingoscillation to said feed lift shaft, said cam follower means comprisinga crank arm on said feed lift shaft, a pin mounted in said crank arm onan axis parallel to the axis of said feed lift shaft, a cam followerelement carried by said pin and engaging said cam surface, said camfollower element having a cam engaging surface that is arcuate in adirection radially of said cam and is defined by straight parallel linesin a direction perpendicular to the radius of said cam surface.

15 References Cited in the file of this patent UNITED STATES PATENTS1,612,500 Ezbelent et a1. Dec. 28, 1926 2,808,793 Ay es Oct. 8, 1957 202.899.920 Dunn Aug. 18, 1959

